1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus and a process cartridge capable of being mounted in the electrophotographic image forming apparatus.
2. Description of Related Art
Conventional image forming apparatuses using electrophotographic image forming processes employ a process cartridge system in which an electrophotographic photosensitive body and processing means working on the electrophotographic photosensitive body are integrally made to be a cartridge that is detachably attachable to the main body of the image forming apparatus. Because the process cartridge system makes it possible for a user to perform the maintenance of the image forming apparatus by himself or herself without asking a service person to maintain the apparatus, the system can remarkably improve the operability of the apparatus. Consequently, the process cartridge system is widely used in an image forming apparatus.
In such a process cartridge, a first frame body for rotatably supporting a developing roller being roller-like developing means and a second frame body for rotatably supporting a photosensitive body drum being a cylindrical electrophotographic photosensitive body are rotatably assembled with each other, and the photosensitive body drum and the developing roller are alongside disposed while keeping a small gap by a spacer, while also being biased to approach each other by a compressed coil spring or the like. Moreover, the first frame body includes a toner containing portion for containing toner being a developer, and the second frame body includes charging means and cleaning means. As the charging means, the so-called contact charging apparatus, which charges the surface of the photosensitive body drum uniformly by applying a voltage to a charging member contacting with the photosensitive body drum directly, has been proposed and practically used.
A representative contact charging apparatus is a roller charging apparatus. The roller (or a charging roller) generally includes a conductive base roller and a middle resistive layer formed on the surface of the base roller, and the roller follows the rotation of the photosensitive body drum and rotates in accordance with the rotation of the photosensitive body drum. A predetermined voltage is applied between the charging roller and the photosensitive body drum, and thereby the surface of the photosensitive body drum is charged at a uniform electric potential. Incidentally, the charging roller biased by a compressed coil spring or the like is in contact with the photosensitive body drum with a predetermined amount of nip.
On the other hand, the cleaning means generally touches a cleaning blade made of an elastic member of urethane or the like to the photosensitive body drum, and the cleaning blade scrapes residual toner on the photosensitive body drum to remove the residual toner from the photosensitive body drum. The scraped toner is collected into a waste toner containing portion in the second frame body. Moreover, the process cartridge is usually hermetically contained in a packing bag made of a light shielding sheet lest the photosensitive body drum should be exposed to outside light for a long time. In such a state, the process cartridge is usually housed in a packing case to be shipped. That is, in a process cartridge not used yet, the charging roller, the cleaning blade, and the like abut the surface of the photosensitive body drum at nearly the same position from the time when the process cartridge has been shipped to the time when the process cartridge is used.
However, in the case where the process cartridge is transported in the state mentioned above, stresses such as frictional force and the like caused by vibrations, impact and the like are applied to the portion of the photosensitive body drum where the charging roller and the cleaning blade abut, so that the photosensitive body drum is sometimes charged.
In many cases, the process cartridge is left as it is for a certain period, and the charge is naturally discharged. However, if the process cartridge is left as it is for a long time in the state such that the charging roller and the like abuts against the charged portion, the charge is not naturally discharged and is instead memorized on the photosensitive body drum sometimes. Consequently, a black streak or a white streak is produced on a formed image owing to the memorized charge.
The present invention was made for solving the aforesaid problem. An object of the invention is to provide an electrophotographic image forming apparatus and a process cartridge, both being able to prevent the occurrence of an image defect such as a black streak at the initial state of the process cartridge owing to the charging of the surface of an electrophotographic photosensitive body caused by frictional forces and the like arising from vibrations and impact during the transportation of the process cartridge.
Another object of the invention is to provide an electrophotographic image forming apparatus and a process cartridge, both being able to prevent the occurrence of image defects at the initial state of the process cartridge by judging whether the process cartridge is new or not and then by controlling the charge elimination operation of the surface of an electrophotographic photosensitive body on the basis of the judgment.
An image forming apparatus according to the present invention is an electrophotographic image forming apparatus, which is able to mount a process cartridge detachably, for forming an image on a recording medium, and the electrophotographic image forming apparatus includes mounting means for making the process cartridge detachably mountable, the process cartridge including an electrophotographic photosensitive body, processing means having at least either of charging means for charging the electrophotographic photosensitive body and cleaning means for cleaning the electrophotographic photosensitive body, and storing means for storing information; transporting means for transporting the recording medium; controlling means for controlling an operation of the electrophotographic image forming apparatus to execute reading and/or writing of the information to the storing means; and exposing means for exposing the electrophotographic photosensitive body to light, wherein the controlling means controls a charge elimination operation of the electrophotographic photosensitive body on a basis of the information in the storing means.
Moreover, a process cartridge according to the present invention is a process cartridge mountable in a main body of an electrophotographic image forming apparatus detachably, and the process cartridge includes an electrophotographic photosensitive body; charging means for charging a surface of the electrophotographic photosensitive body; cleaning means for cleaning the electrophotographic photosensitive body, and storing means for storing information, the storing means also storing a piece of information for controlling a charge elimination operation of the electrophotographic photosensitive body when the process cartridge is mounted in the main body of the electrophotographic image forming apparatus.
The present invention can prevent the occurrence of image defects such as a black streak at the initial state of a process cartridge owing to the charging of the surface of an electrophotographic photosensitive body caused by, for example, frictional forces and the like brought about by vibrations, and impact during the transportation of the process cartridge.